The present invention relates to a screwdriver bit assembly with a magnetic structure and, more particularly, to a screwdriver bit assembly with a magnetic structure for reliably attracting a screw for the purposes of increasing operational stability.
A conventional screwdriver bit generally includes a shank having a front end with an insertion end in the form of a Phillips head tip, a cabinet tip, or a polygonal tip. The insertion end of the screwdriver bit can be coupled with a correspondingly shaped groove in an end of a screw, and the screwdriver bit can be rotated to tighten or loosen the screw. To permit easy operation, the insertion end of the screwdriver bit is provided with magnetism for attracting the screw. However, the attracting force provided by the screwdriver bit is weak, such that the screw is apt to fall off when the screwdriver bit wobbles.
In an approach to solve the above disadvantage, a sleeve is mounted on the front end of the screwdriver bit. The sleeve includes a hole through which the screwdriver bit extends. A magnetic member is mounted to a front end of the sleeve. The sleeve is generally made of a plastic material having low magnetic conductivity to avoid larger magnetism on the outer periphery of the sleeve. After the sleeve is mounted on the front end of the screwdriver bit, the magnetic member on the front end of the sleeve can absorb a screw to provide convenient operation.
FIG. 8 shows a structure disclosed by Taiwan Invention Patent No. I254660. The structure a plastic sleeve 1′, a magnetic member 2′, and a screwdriver bit 3′. The sleeve 1′ includes a central hole 11′ having a reduced coupling section 12′ at a rear end thereof. The magnetic member 2′ is mounted to the front end of the sleeve 1′ and includes a through-hole 21′ having a diameter smaller than a diameter of the central hole 11′. The screwdriver bit 3′ extends through the central hole 11′ and the through-hole 21′. The screwdriver bit 3′ includes a reduced portion 31′ engaged in the reduced coupling section 12′ to restrain movement of the sleeve 1′, preventing the sleeve 1′ from disengaging from the screwdriver bit 3′.
In use, the magnetic member 2′ attracts the screw 4′ to provide secure engagement between the front end of the screwdriver bit 3′ and the screw 4′. However, the sleeve 1′ engages with the reduced portion 31′ of the screwdriver bit 3′ merely by the reduced coupling section 12′, providing insufficient engagement stability. In a case that the screwdriver bit 3′ is driven by a high-speed electric tool to threadedly fix the screw 4′ into a workpiece 5′, no stopping mechanism is provided between the sleeve 1′ and the screwdriver bit 3′, such that the screwdriver bit 3′ and the screw 4′ could move further forward into the workpiece 5′ due to inadvertent operation or vibrations. The screwdriver bit 3′ could move forward relative to the sleeve 1′ (see the arrow in FIG. 8), such that the screw 4′ cannot be reliably attracted by the magnetic member 2′ on the sleeve 1′ and such that the workpiece 5′ could be damaged.